The Urinary 1-hydroxypyrene Biomarker in Street Janitors Exposed to Traffic Related Benzo[a]Pyrene During One Islamic Calendar Year in Madinah, Saudi Arabia

Abstract

Background Madinah is the second most important Muslim holy city in Saudi Arabia. Therefore, during the holy months, traffic congestion and consequent air emission of several pollutant compounds, mainly carcinogenic Benzo[a]pyrene (BaP), are expected to reach high levels in certain places. The emission of these pollutants into the atmosphere increases their concentration, which in turn increases the risk of exposure through inhalation. Inhalation of air BaP is the main route of entry into the human body, and so the aim of the present study was to assess exposure to air BaP through urinary 1-hydroxypyrene (1-OHP) in street janitors. The study also aimed at finding the relation between this biomarker and daily exposure to air BaP with traffic volume and meteorological factors, such as wind speed, temperature, wind direction, relative humidity, and precipitation. Methods The study was performed during one Islamic calendar year from 1/4/1438 – 30/3/1439 (December 2016 to November 2017) in Madinah City. The research was designed to include three traffic locations with high traffic density and two control locations with low traffic activity. In these locations, BaP was measured daily in the breathing-zone air of the street janitors using PM2.5 personal samplers, and in the air of the five studied locations using high-volume air samplers. Daily measures including traffic volume (cars, medium and heavy vehicles), temperature, humidity, wind speed, and precipitation, were recorded at the five studied locations. 20 male participants (street janitors) aged between 25 and 35 years were recruited in the study from each of the five studied locations. In total, 100 street janitors were involved in the study. Two urine samples were obtained from each participant after their work shift and in the early morning of the next day to measure 1- OHP. Summary statistics, including medians, were used to describe the data. Graphs, including II calendar and time series plots were used to visually present the data. Data were analysed using methods that included Spearman’s rank correlation, Mann-Whitney, and Kruskal-Wallis tests. Results It was found that BaP and 1-OHP concentrations were significantly higher in the heavy traffic locations compared to the control locations. The research also found that BaP and 1-OHP concentrations were significantly higher during the holy months of the Islamic calendar than the normal months. For example, the median concentrations of 1-OHP in traffic locations during the holy months of Ramadan, Dhu al-Qadah, Dhu al-Ḥijjah and Muḥarram were 0.98, 0.99, 1.01 and 0.82 μmol/mol, respectively. The median concentrations of 1-OHP in normal months ranged between 0.71–0.74 μmol/mol. The median ambient BaP concentration during the holy months ranged between 0.59–0.63 ng/m3 , while in the normal months it ranged between 0.36–0.39 ng/m3 . It was also found that morning 1-OHP concentration was higher than after work 1-OHP concentration. The research also found that ambient BaP concentration was generally higher than the individual BaP concentration. Correlation results indicated that ambient BaP is positively correlated with CO (r = 0.59, p<0.001) and traffic volume (r = 0.74, p<0.001. It was also found that individual BaP is positively correlated with CO (r = 0.56, p<0.001) and traffic volume (r = 0.85, p<0.001). Meteorological conditions such as temperature, relative humidity and precipitation were found to have no effect on the concentration of both ambient and individual BaP. Conclusion The research found that the higher the traffic volume in Madinah, especially during the holy months, the higher the ambient BaP pollutants, and the higher the chance of people being exposed to BaP pollutants (individual BaP). Therefore, it is recommended that efforts to reduce the number of vehicles in Madinah be adopted. Two approaches are suggested: enacting laws preventing traffic, tax law in traffic areas to reduce the number of cars in the traffic areas, and encouraging the use of hybrid buses, electric trains and cars in Madinah. It is, however, important to note that the higher correlations found in this study were likely due to the controlled environment.